Is a Machine More Efficient Than the Hand?

What are the washing-up techniques that can transform a consumer from a carefree dishwasher to a supereconomic one?

In seeking to understand and prevent global warming and other man-made environmental problems, the energy consumption of household appliances has come under close scrutiny. One household task—dishwashing—can be accomplished by an appliance, by hand, or by some combination of the two.To investigate the environmental effects of these competing methods, I and a team of researchers from the University of Bonn conducted a test comparing the energy consumption and performance of manual dishwashing with that of dishwashing machines. To rule out possible regional differences in dishwashing techniques, we persuaded 113 people from seven countries in Europe to participate in the dishwashing experiment.We compared their use of water and energy and the cleanliness they achieved to the consumption generated by two energyefficient dishwashers.To reduce variability in test conditions,we had most of the test subjects wash dishes in one laboratory at the University of Bonn. For test subjects,we chose visitors who had not lived for too long in Bonn or Germany to ensure that they had not adopted German behavior.To make sure that we were getting a correct picture of the consumer ...